Ultraviolet radiation (biology)
Giese, Arthur C. Department of Biological Sciences, Stanford University, Stanford, California.
Last reviewed:July 2018
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- Photobiological effects
- Action spectra
- Effects on the skin
- Clinical use
- Links to Primary Literature
- Additional Readings
Electromagnetic radiation in the wavelength range of 10 to 400 nanometers that affects biological organisms. The ultraviolet (UV) portion of the electromagnetic spectrum includes all radiations from 10 to 400 nanometers (nm); in addition, radiations as low as 4 nm are sometimes included in this range. Radiations shorter than 200 nm are absorbed by most substances, even by air; therefore, they are technically difficult to use in biological experimentation. Radiations between 200 and 320 nm are selectively absorbed by organic matter, and they produce the best-known effects of ultraviolet radiations in organisms. Radiations between 320 and 400 nm are relatively little absorbed and are less active on organisms. In general, though, ultraviolet radiation in sunlight at the surface of the Earth is restricted to the span from about 290 to 400 nm as a result of the protective effects of the Earth's ozone layer. Notably, and in contrast to x-rays, ultraviolet radiations do not penetrate far into larger organisms; thus, the effects that they produce are surface effects, such as sunburn and development of D vitamins from precursors present in skin or fur. Moreover, excessive exposure to the ultraviolet rays in sunlight can cause skin cancer (Fig. 1). See also: Cancer; Electromagnetic radiation; Radiation biology; Radiation injury (biology); Stratospheric ozone; Ultraviolet radiation; Vitamin D
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